Imaging lens

ABSTRACT

There is provided an imaging lens with excellent optical characteristics which satisfies demand of a low profile and a low F-number. An imaging lens comprises in order from an object side to an image side, a first lens with positive refractive power having an object-side surface being convex in a paraxial region; a second lens with negative refractive power having an object-side surface being convex in a paraxial region; a third lens with negative refractive power having an object-side surface being concave in a paraxial region; a fourth lens with negative refractive power in a paraxial region; and a fifth lens with positive refractive power having an image-side surface being convex in a paraxial region, and predetermined conditional expressions are satisfied.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an imaging lens which forms an image of an object on a solid-state image sensor such as a CCD sensor or a C-MOS sensor used in an imaging device.

Description of the Related Art

In recent years, it becomes common that camera function is mounted in various products, such as information terminal equipment, home appliances, automobiles, and the like.

Development of products with the camera function will be made accordingly.

The imaging lens mounted in such equipment is required to be compact and to have high-resolution performance.

As a conventional imaging lens aiming high performance, for example, the imaging lens disclosed in the following Patent Document 1 has been known.

Patent Document 1 (CN108152936A) discloses an imaging lens comprising, in order from an object side: a first lens with positive refractive power having a convex object-side surface; a second lens with negative refractive power, being formed in a meniscus shape having a convex object-side surface; a third lens with negative refractive power having a concave image-side surface; a fourth lens with positive refractive power, being formed in a biconvex shape having a convex object-side surface; and a fifth lens with negative refractive power, being formed in a meniscus shape having a concave object-side surface; and a relationship between a total track length and a focal length of the overall optical system satisfies a certain condition.

SUMMARY OF THE INVENTION

However, in lens configurations disclosed in the Patent Document 1, when a low profile and a low F-number are to be realized, it is very difficult to correct aberrations at a peripheral area, and excellent optical performance can not be obtained.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an imaging lens with high resolution which satisfies demand of the low profile and the low F-number in well balance and excellently corrects aberrations.

Regarding terms used in the present invention, “a convex surface (a surface being convex)”, “a concave surface (a surface being concave)” or “a flat surface (a surface being flat)” of lens surfaces implies a shape of the lens surface in a paraxial region (near the optical axis). “Refractive power” implies the refractive power in a paraxial region. “A pole point” implies an off-axial point on an aspheric surface at which a tangential plane intersects the optical axis perpendicularly. “A total track length” is defined as a distance along the optical axis from an object-side surface of an optical element located closest to the object to an image plane. “The total track length” and “a back focus” is a distance obtained when thickness of an IR cut filter or a cover glass which may be arranged between the imaging lens and the image plane is converted into an air-converted distance.

An imaging lens according to the present invention comprises, in order from an object side to an image side; a first lens with positive refractive power having an object-side surface being convex in a paraxial region; a second lens with negative refractive power having an object-side surface being convex in a paraxial region; a third lens with negative refractive power having an object-side surface being concave in a paraxial region; a fourth lens with negative refractive power in a paraxial region; and a fifth lens with positive refractive power having an image-side surface being convex in a paraxial region.

The first lens achieves reduction in a profile of the imaging lens by strengthening the refractive power. Furthermore, when the first lens has the object-side surface being convex in the paraxial region, spherical aberration, coma aberration, and distortion are properly suppressed.

The second lens properly corrects chromatic aberration, the spherical aberration, the coma aberration, astigmatism, field curvature, and the distortion. Furthermore, when the second lens has the object-side surface being convex in the paraxial region, the spherical aberration, the coma aberration, and the astigmatism are properly corrected.

The third lens properly corrects the chromatic aberration, the coma aberration, the astigmatism, and the distortion. Furthermore, when the third lens has the object-side surface being concave in the paraxial region, the coma aberration and the distortion are properly corrected.

The fourth lens properly corrects the coma aberration, the astigmatism, the field curvature, and the distortion.

The fifth lens achieves reduction in the profile of the imaging lens, and properly corrects the spherical aberration, the coma aberration, the astigmatism, the field curvature, and the distortion. Furthermore, when the fifth lens has the image-side surface being convex in the paraxial region, a light ray incident angle to an image sensor can be appropriately controlled.

As a result, a lens diameter of the fifth lens can be reduced and reduction in a diameter of the imaging lens can be achieved.

According to the imaging lens having the above-described configuration, it is preferable that an image-side surface of the first lens is concave in the paraxial region.

When the image-side surface of the first lens is concave in the paraxial region, the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that an image-side surface of the second lens is concave in the paraxial region.

When the image-side surface of the second lens is concave in the paraxial region, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that an image-side surface of the third lens is convex in the paraxial region.

When the image-side surface of the third lens is convex in the paraxial region, the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that an image-side surface of the fourth lens is concave in the paraxial region.

When the image-side surface of the fourth lens is concave in the paraxial region, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (1) is satisfied:

0.90<|r7|/f<4.00  (1)

where

r7: a paraxial curvature radius of an object-side surface of the fourth lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (1) defines an appropriate range of the paraxial curvature radius of the object-side surface of the fourth lens. By satisfying the conditional expression (1), the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (2) is satisfied:

0.15<r3/f<0.75  (2)

where

r3: a paraxial curvature radius of an object-side surface of the second lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (2) defines an appropriate range of the paraxial curvature radius of the object-side surface of the second lens. By satisfying the conditional expression (2), the coma aberration and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (3) is satisfied:

1.00<r4/T2<5.25  (3)

where

r4: a paraxial curvature radius of an image-side surface of the second lens, and

T2: a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens.

The conditional expression (3) defines an appropriate range of a relationship between the paraxial curvature radius of the image-side surface of the second lens and the distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens. By satisfying the conditional expression (3), the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (4) is satisfied:

−12.00<r5/D3<−3.00  (4)

where

r5: a paraxial curvature radius of an object-side surface of the third lens, and

D3: a thickness along the optical axis of the third lens.

The conditional expression (4) defines an appropriate range of a relationship between the paraxial curvature radius of the object-side surface of the third lens and the thickness along the optical axis of the third lens. By satisfying the conditional expression (4), reduction in the profile can be achieved, and the coma aberration and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (5) is satisfied:

0.40<r3/r4<1.80  (5)

where

r3: a paraxial curvature radius of an object-side surface of the second lens, and

r4: a paraxial curvature radius of an image-side surface of the second lens.

The conditional expression (5) defines an appropriate range of a relationship between the paraxial curvature radius of the object-side surface of the second lens and the paraxial curvature radius of the image-side surface of the second lens. By satisfying the conditional expression (5), the spherical aberration, the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (6) is satisfied:

9.00<r2/f  (6)

where

r2: a paraxial curvature radius of an image-side surface of the first lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (6) defines an appropriate range of the paraxial curvature radius of the image-side surface of the first lens. By satisfying the conditional expression (6), the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (7) is satisfied:

−7.00<r6/f<−1.50  (7)

where

r6: a paraxial curvature radius of an image-side surface of the third lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (7) defines an appropriate range of the paraxial curvature radius of the image-side surface of the third lens. By satisfying the conditional expression (7), the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (8) is satisfied:

0.20<r8/f<1.10  (8)

where

r8: a paraxial curvature radius of an image-side surface of the fourth lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (8) defines an appropriate range of the paraxial curvature radius of the image-side surface of the fourth lens. By satisfying the conditional expression (8), the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (9) is satisfied:

−1.00<r10/f<−0.25  (9)

where

r10: a paraxial curvature radius of an image-side surface of the fifth lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (9) defines an appropriate range of the paraxial curvature radius of the image-side surface of the fifth lens. By satisfying the conditional expression (9), the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (10) is satisfied:

400.00<r2/r1/T1  (10)

where

r2: a paraxial curvature radius of an image-side surface of the first lens,

r1: a paraxial curvature radius of an object-side surface of the first lens, and

T1: a distance along the optical axis from an image-side surface of the first lens to an object-side surface of the second lens.

The conditional expression (10) defines an appropriate range of a relationship among the paraxial curvature radius of the image-side surface of the first lens, the paraxial curvature radius of the object-side surface of the first lens, and the distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens. By satisfying the conditional expression (10), the spherical aberration, the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (11) is satisfied:

20.00<r2/r3  (11)

where

r2: a paraxial curvature radius of an image-side surface of the first lens, and

r3: a paraxial curvature radius of an object-side surface of the second lens.

The conditional expression (11) defines an appropriate range of a relationship between the paraxial curvature radius of the image-side surface of the first lens and the paraxial curvature radius of the object-side surface of the second lens. By satisfying the conditional expression (11), the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (12) is satisfied:

r2/r3/r10<−2.00  (12)

where

r2: a paraxial curvature radius of an image-side surface of the first lens,

r3: a paraxial curvature radius of an object-side surface of the second lens, and

r10: a paraxial curvature radius of an image-side surface of the fifth lens.

The conditional expression (12) defines an appropriate range of a relationship among the paraxial curvature radius of the image-side surface of the first lens, the paraxial curvature radius of the object-side surface of the second lens, and the paraxial curvature radius of the image-side surface of the fifth lens. By satisfying the conditional expression (12), the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (13) is satisfied:

0.10<r3/|r7|<0.80  (13)

where

r3: a paraxial curvature radius of an object-side surface of the second lens, and

r7: a paraxial curvature radius of an object-side surface of the fourth lens.

The conditional expression (13) defines an appropriate range of a relationship between the paraxial curvature radius of the object-side surface of the second lens and the paraxial curvature radius of the object-side surface of the fourth lens. By satisfying the conditional expression (13), the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (14) is satisfied:

0.05<r5/r6<0.25  (14)

where

r5: a paraxial curvature radius of an object-side surface of the third lens, and

r6: a paraxial curvature radius of an image-side surface of the third lens.

The conditional expression (14) defines an appropriate range of a relationship between the paraxial curvature radius of the object-side surface of the third lens and the paraxial curvature radius of the image-side surface of the third lens. By satisfying the conditional expression (14), the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (15) is satisfied:

−0.65<r5/|r7|<−0.10  (15)

where

r5: a paraxial curvature radius of an object-side surface of the third lens, and

r7: a paraxial curvature radius of an object-side surface of the fourth lens.

The conditional expression (15) defines an appropriate range of a relationship between the paraxial curvature radius of the object-side surface of the third lens and the paraxial curvature radius of the object-side surface of the fourth lens. By satisfying the conditional expression (15), the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (16) is satisfied:

0.10<r8/|r7|<1.00  (16)

where

r8: a paraxial curvature radius of an image-side surface of the fourth lens, and

r7: a paraxial curvature radius of an object-side surface of the fourth lens.

The conditional expression (16) defines an appropriate range of a relationship between the paraxial curvature radius of the image-side surface of the fourth lens and the paraxial curvature radius of the object-side surface of the fourth lens. By satisfying the conditional expression (16), the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (17) is satisfied:

−2.60<r10/r3<−0.90  (17)

where

r10: a paraxial curvature radius of an image-side surface of the fifth lens, and

r3: a paraxial curvature radius of an object-side surface of the second lens.

The conditional expression (17) defines an appropriate range of a relationship between the paraxial curvature radius of the image-side surface of the fifth lens and the paraxial curvature radius of the object-side surface of the second lens. By satisfying the conditional expression (17), the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (18) is satisfied:

−4.00<r10/r4<−1.55  (18)

where

r10: a paraxial curvature radius of an image-side surface of the fifth lens, and

r4: a paraxial curvature radius of an image-side surface of the second lens.

The conditional expression (18) defines an appropriate range of a relationship between the paraxial curvature radius of the image-side surface of the fifth lens and the paraxial curvature radius of the image-side surface of the second lens. By satisfying the conditional expression (18), the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (19) is satisfied:

−1.40<f3/f<−0.40  (19)

where

f3: a focal length of the third lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (19) defines an appropriate range of the focal length of the third lens. By satisfying the conditional expression (19), the chromatic aberration, the coma aberration, the astigmatism, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (20) is satisfied:

0.40<f5/f<1.30  (20)

where

f5: a focal length of the fifth lens, and

f: a focal length of the overall optical system of the imaging lens.

The conditional expression (20) defines an appropriate range of the focal length of the fifth lens. By satisfying the conditional expression (20), reduction in the profile can be achieved, and the spherical aberration, the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (21) is satisfied:

3.00<f5/D5<12.50  (21)

where

f5: a focal length of the fifth lens, and

D5: a thickness along the optical axis of the fifth lens.

The conditional expression (21) defines an appropriate range of a relationship between the focal length of the fifth lens and the thickness along the optical axis of the fifth lens. By satisfying the conditional expression (21), reduction in the low profile can be achieved, and the spherical aberration, the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (22) is satisfied:

−3.00<f2/f5<−1.00  (22)

where

f2: a focal length of the second lens, and

f5: a focal length of the fifth lens.

The conditional expression (22) defines an appropriate range of a relationship between the focal length of the second lens and the focal length of the fifth lens. By satisfying the conditional expression (22), reduction in the low profile can be achieved, and the chromatic aberration, the spherical aberration, the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

According to the imaging lens having the above-described configuration, it is preferable that the following conditional expression (23) is satisfied:

−0.43<(f4/f)+(f5/f)<0.00  (23)

where

f4: a focal length of the fourth lens,

f: a focal length of the overall optical system of the imaging lens, and

f5: a focal length of the fifth lens.

The conditional expression (23) defines an appropriate range of a relationship among the focal length of the fourth lens, the focal length of the overall optical system of the imaging lens, and the focal length of the fifth lens. By satisfying the conditional expression (23), reduction in the low profile can be achieved, and the spherical aberration, the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

Effect of Invention

According to the present invention, there can be provided an imaging lens with high resolution which satisfies demand of the low profile and the low F-number in well balance, and properly corrects aberrations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an imaging lens in Example 1 according to the present invention.

FIG. 2 shows spherical aberration, astigmatism, and distortion of the imaging lens in Example 1 according to the present invention.

FIG. 3 is a schematic view showing an imaging lens in Example 2 according to the present invention.

FIG. 4 shows spherical aberration, astigmatism, and distortion of the imaging lens in Example 2 according to the present invention.

FIG. 5 is a schematic view showing an imaging lens in Example 3 according to the present invention.

FIG. 6 shows spherical aberration, astigmatism, and distortion of the imaging lens in Example 3 according to the present invention.

FIG. 7 is a schematic view showing an imaging lens in Example 4 according to the present invention.

FIG. 8 shows spherical aberration, astigmatism, and distortion of the imaging lens in Example 4 according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the preferred embodiment of the present invention will be described in detail referring to the accompanying drawings.

FIGS. 1, 3, 5 and 7 are schematic views of the imaging lenses in Examples 1 to 4 according to the embodiments of the present invention, respectively.

The imaging lens according to the present invention comprises, in order from an object side to an image side, a first lens L1 with positive refractive power having an object-side surface being convex in a paraxial region; a second lens L2 with negative refractive power having an object-side surface being convex in a paraxial region; a third lens L3 with negative refractive power having an object-side surface being concave in a paraxial region; a fourth lens L4 with negative refractive power in a paraxial region; and a fifth lens L5 with positive refractive power having an image-side surface being convex in a paraxial region.

A filter IR such as an IR cut filter and a cover glass are arranged between the fifth lens L5 and an image plane IMG (namely, the image plane of an image sensor). The filter IR is omissible.

By arranging an aperture stop ST on the object side of the first lens L1, correction of aberrations and control of an incident angle of the light ray of high image height to an image sensor become facilitated.

The first lens L1 has the positive refractive power and is formed in a meniscus shape having the object-side surface being convex and an image-side surface being concave in a paraxial region (near the optical axis X). Therefore, reduction in a profile is achieved by strengthening the refractive power. Furthermore, when the first lens L1 has the object-side surface being convex in the paraxial region, the spherical aberration, the coma aberration, and distortion are suppressed

The second lens L2 has the negative refractive power and is formed in a meniscus shape having the object-side surface being convex and an image-side surface being concave in a paraxial region (near the optical axis X). Therefore, chromatic aberration, the spherical aberration, the coma aberration, astigmatism, field curvature, and the distortion are properly corrected. Furthermore, when the second lens L2 has the object-side surface being convex in the paraxial region, the spherical aberration, the coma aberration, and the astigmatism are more properly corrected.

The third lens L3 has the negative refractive power and is formed in a meniscus shape having the object-side surface being concave and an image-side surface being convex in a paraxial region (near the optical axis X). Therefore, the chromatic aberration, the coma aberration, the astigmatism, and the distortion are properly corrected. Furthermore, when the third lens L3 has the object-side surface being concave in the paraxial region, the coma aberration and the distortion are more properly corrected.

The image-side surface of the third lens L3 is formed as an aspheric surface having at least one pole point in a position off the optical axis X. Therefore, the astigmatism and the distortion are more properly corrected.

The fourth lens L4 has the negative refractive power and is formed in a meniscus shape having the object-side surface being convex and an image-side surface being concave in a paraxial region (near the optical axis X). Therefore, the coma aberration, the astigmatism, the field curvature, and the distortion are properly corrected.

The fourth lens L4 may be formed in a biconcave shape having the object-side surface and the image-side surface being both concave in the paraxial region (near the optical axis X) as in the Examples 2, 3, and 4 shown in FIGS. 3, 5, and 7. In this case, the chromatic aberration is favorably corrected by the negative refractive powers on both sides.

The image-side surface of the fourth lens L4 is formed as an aspheric surface having at least one pole point in a position off the optical axis X. Therefore, the astigmatism, the field curvature, and the distortion are more properly corrected.

The fifth lens L5 has positive refractive power and is formed in a biconvex shape having an object-side surface and the image-side surface being convex in a paraxial region. Therefore, reduction in a profile can be achieved, and the spherical aberration, the coma aberration, the astigmatism, the field curvature, and the distortion are properly corrected. Furthermore, when the fifth lens L5 has the image-side surface being convex in the paraxial region, a light ray incident angle to an image sensor can be appropriately controlled. As a result, a lens diameter of the fifth lens L5 can be reduced and reduction in a diameter of the imaging lens can be achieved.

The fifth lens L5 may be formed in a meniscus shape having the object-side surface being concave and the image-side surface being convex in the paraxial region as in the Examples 2 and 3 shown in FIGS. 3 and 5. In this case, the astigmatism, the field curvature, and the distortion can be properly corrected. Furthermore, the fifth lens L5 may be formed in a plano-convex shape having the object-side surface being flat and the image-side surface being convex. In this case, the coma aberration, the astigmatism, the field curvature, and the distortion can be properly corrected.

Regarding the imaging lens according to the present embodiments, it is preferable that all lenses of the first lens L1 to the fifth lens L5 are single lenses. Configuration only with the single lenses can frequently use the aspheric surfaces. In the present embodiments, all lens surfaces are formed as appropriate aspheric surfaces, and the aberrations are favorably corrected. Furthermore, in comparison with the case in which a cemented lens is used, workload is reduced, and manufacturing in low cost becomes possible.

Furthermore, the imaging lens according to the present embodiments makes manufacturing facilitated by using a plastic material for all lenses, and mass production in a low cost can be realized.

The material applied to the lens is not limited to the plastic material. By using glass material, further high performance may be aimed. It is preferable that all of lens-surfaces are formed as aspheric surfaces, however, spherical surfaces easy to be manufactured may be adopted in accordance with required performance.

The imaging lens according to the present embodiments shows preferable effect by satisfying the following conditional expressions (1) to (23).

0.90<|r7|/f<4.00  (1)

0.15<r3/f<0.75  (2)

1.00<r4/T2<5.25  (3)

−12.00<r5/D3<−3.00  (4)

0.40<r3/r4<1.80  (5)

9.00<r2/f  (6)

−7.00<r6/f<−1.50  (7)

0.20<r8/f<1.10  (8)

−1.00<r10/f<−0.25  (9)

400.00<r2/r1/T1  (10)

20.00<r2/r3  (11)

r2/r3/r10<−2.00  (12)

0.10<r3/|r7|<0.80  (13)

0.05<r5/r6<0.25  (14)

−0.65<r5/|r7|<−0.10  (15)

0.10<r8/|r7|<1.00  (16)

−2.60<r10/r3<−0.90  (17)

−4.00<r10/r4<−1.55  (18)

−1.40<f3/f<−0.40  (19)

0.40<f5/f<1.30  (20)

3.00<f5/D5<12.50  (21)

−3.00<f2/f5<−1.00  (22)

−0.43<(f4/f)+(f5/f)<0.00  (23)

where

D3: a thickness along the optical axis X of the third lens L3,

D5: a thickness along the optical axis X of the fifth lens L5,

T1: a distance along the optical axis X from an image-side surface of the first lens L1 to an object-side surface of the second lens L2,

T2: a distance along the optical axis X from an image-side surface of the second lens L2 to an object-side surface of the third lens L3,

f: a focal length of the overall optical system of the imaging lens,

f2: a focal length of the second lens L2,

f3: a focal length of the third lens L3,

f4: a focal length of the fourth lens L4,

f5: a focal length of the fifth lens L5,

r1: a paraxial curvature radius of an object-side surface of the first lens L1,

r2: a paraxial curvature radius of an image-side surface of the first lens L1,

r3: a paraxial curvature radius of an object-side surface of the second lens L2,

r4: a paraxial curvature radius of an image-side surface of the second lens L2,

r5: a paraxial curvature radius of an object-side surface of the third lens L3,

r6: a paraxial curvature radius of an image-side surface of the third lens L3,

r7: a paraxial curvature radius of an object-side surface of the fourth lens L4,

r8: a paraxial curvature radius of an image-side surface of the fourth lens L4, and

r10: a paraxial curvature radius of an image-side surface of the fifth lens L5.

It is not necessary to satisfy the above all conditional expressions, and by satisfying the conditional expression individually, operational advantage corresponding to each conditional expression can be obtained.

The imaging lens according to the present embodiments shows further preferable effect by satisfying the following conditional expressions (1a) to (23a).

1.00<|r7|/f<3.00  (1a)

0.25<r3/f<0.55  (2a)

2.10<r4/T2<4.65  (3a)

−10.00<r5/D3<−5.00  (4a)

0.95<r3/r4<1.65  (5a)

12.50<r2/f<300.00  (6a)

−5.50<r6/f<−2.00  (7a)

0.30<r8/f<0.95  (8a)

−0.75<r10/f<−0.40  (9a)

625.00<r2/r1/T1<11000.00  (10a)

35.00<r2/r3<700.00  (11a)

−200.00<r2/r3/r10<−6.00  (12a)

0.15<r3/|r7|<0.55  (13a)

0.08<r5/r6<0.20  (14a)

−0.50<r5/|r7|<−0.15  (15a)

0.20<r8/|r7|<0.85  (16a)

−2.10<r10/r3<−1.20  (17a)

−3.00<r10/r4<−2.00  (18a)

−1.05<f3/f<−0.60  (19a)

0.60<f5/f<1.10  (20a)

5.00<f5/D5<10.00  (21a)

−2.25<f2/f5<−1.20  (22a)

−0.25<(f4/f)+(f5/f)<0.00  (23a)

The signs in the above conditional expressions have the same meanings as those in the paragraph before the preceding paragraph.

In this embodiment, the aspheric shapes of the aspheric surfaces of the lens are expressed by Equation 1, where Z denotes an axis in the optical axis direction, H denotes a height perpendicular to the optical axis, R denotes a paraxial curvature radius, k denotes a conic constant, and A4, A6, A8, A10, A12, A14, A16, A18 and A20 denote aspheric surface coefficients.

$\begin{matrix} {Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {\left( {k + 1} \right)\frac{H^{2}}{R}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}} + {A_{18}H^{18}} + {A_{20}H^{20}}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \end{matrix}$

Next, examples of the imaging lens according to this embodiment will be explained. In each example, f denotes a focal length of the overall optical system of the imaging lens, Fno denotes a F-number, ω denotes a half field of view, ih denotes a maximum image height, and TTL denotes a total track length. Additionally, i denotes a surface number counted from the object side, r denotes a paraxial curvature radius, d denotes a distance between lenses along the optical axis (surface distance), Nd denotes a refractive index at d-ray (reference wavelength), and vd denotes an abbe number at d-ray. As for aspheric surfaces, an asterisk (*) is added after surface number i.

Example 1

The basic lens data is shown below in Table 1.

TABLE 1 Example 1 Unitmm f = 8.11 Fno = 2.40 ω(°) = 17.5 h = 2.56 TTL = 7.13 Surface Data i r d Nd ιd (Object) Infinity Infinity 1 (Stop) Infinity −0.8181 2* 1.9042 1.1907 1.535 55.69 (ιd1) 3* 1451.4820 0.0808 4* 3.1488 0.3917 1.671 19.24 (ιd2) 5* 1.9628 0.4859 6* −3.5738 0.4145 1.614 25.59 (ιd3) 7* −36.1750 2.0247 8* 13.2463 0.3400 1.535 55.69 (ιd4) 9* 3.0044 0.3755 10*  55.0469 0.8747 1.671 19.24 (ιd5) 11*  −4.7795 0.7099 12  Infinity 0.2100 1.517 64.20 13  Infinity 0.1012 Image Plane ConstituentLens Data Lens StartSurface FocalLength 1 2 3.564 2 4 −8.956 3 6 −6.488 4 8 −7.351 5 10 6.595 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface k −2.264326E−01 1.548297E−02 7.543238E−01 −7.231530E−01 −1.141201E+01 A4  −1.138967E−02 −5.943091E−02 −8.293443E−02 −4.041004E−02 1.481442E−01 A6  4.710091E−02 2.130992E−01 1.640816E−01 1.581639E−01 −5.981454E−01 A8  −9.399819E−02 −3.822886E−01 −1.494988E−01 −3.322999E−01 2.879886E+00 A10 1.172622E−01 4.224537E−01 −8.653903E−02 7.381323E−01 −8.247626E+00 A12 −9.362472E−02 −3.010684E−01 3.902929E−01 −1.009058E+00 1.494147E+01 A14 4.763048E−02 1.386220E−01 −4.401323E−01 8.447449E−01 −1.722685E+01 A16 −1.493843E−02 −3.998518E−02 2.487670E−01 −2.919897E−01 1.227315E+01 A18 2.632889E−03 6.587571E−03 −7.220086E−02 −7.970703E−02 −4.938038E+00 A20 −2.007209E−04 −4.744678E−04 8.602467E−03 6.864608E−02 8.612866E−01 7th Surface 8th Surface 9th Surface 10th Surface 11th Surface k 9.877481E+00 −1.000000E+01 5.385719E−01 7.911292E+00 7.484142E−01 A4  1.318366E−01 −1.150519E−01 −1.405279E−01 6.342125E−03 1.252602E−02 A6  1.234442E−02 8.464915E−02 4.952439E−02 −6.438674E−02 −3.287659E−02 A8  6.839746E−03 −5.450376E−02 1.861292E−03 6.523173E−02 2.252685E−02 A10 −7.328314E−02 3.118906E−02 −1.411069E−02 −3.326206E−02 −7.897519E−03 A12 1.317707E−01 −1.569710E−02 7.606838E−03 9.764386E−03 1.543629E−03 A14 −1.240035E−01 5.947474E−03 −2.191016E−03 −1.685124E−03 −1.609832E−04 A16 5.364793E−02 −1.445605E−03 3.916112E−04 1.642624E−04 7.647268E−06 A18 −8.550010E−03 1.940264E−04 −4.221720E−05 −7.902495E−06 −8.265741E−08 A20 3.225761E−03 −1.080526E−05 2.100217E−06 1.229188E−07 −1.457658E−09

The imaging lens in Example 1 satisfies conditional expressions (1) to (23) as shown in Table 5.

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Example 1. The spherical aberration diagram shows the amount of aberration at each wavelength of F-ray (486 nm), d-ray (588 nm), and C-ray (656 nm). The astigmatism diagram shows the amount of aberration at d-ray on a sagittal image surface S (solid line) and the amount of aberration at d-ray on tangential image surface T (broken line), respectively (same as FIGS. 4, 6 and 8). As shown in FIG. 2, each aberration is corrected excellently.

Example 2

The basic lens data is shown below in Table 2.

TABLE 2 Example 2 Unitmm f = 8.11 Fno = 2.40 ω(°) = 17.5 h = 2.56 TTL = 7.13 Surface Data i r d Nd ιd (Object) Infinity Infinity 1 (Stop) Infinity −0.8062 2* 1.9251 1.2018 1.535 55.69 (ιd1) 3* 143.3499 0.0824 4* 2.5823 0.3179 1.671 19.24 (ιd2) 5* 1.7637 0.5456 6* −3.5700 0.4977 1.614 25.59 (ιd3) 7* −23.7354 2.1147 8* −8.8984 0.3405 1.535 55.69 (ιd4) 9* 5.9717 0.1980 10*  −176.9727 0.8796 1.671 19.24 (ιd5) 11*  −4.2544 0.7100 12  Infinity 0.2100 1.517 64.20 13  Infinity 0.1014 n age Plane ConstituentLens Data Lens StartSurface FocalLength 1 2 3.638 2 4 −9.827 3 6 −6.906 4 8 −6.629 5 10 6.486 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface k −1.890607E−01 1.448191E−02 −3.859441E−01 −1.162909E+00 −9.733415E+00 A4  3.298116E−03 −4.157275E−02 −5.926374E−02 5.243479E−03 8.560153E−02 A6  −1.958502E−03 5.463318E−02 −1.643789E−01 −3.973808E−01 −1.955160E−01 A8  6.713723E−04 5.571191E−03 8.020970E−01 2.066551E+00 1.118916E+00 A10 4.012442E−03 −8.821529E−02 −1.623840E+00 −5.517752E+00 −3.539385E+00 A12 −7.575741E−03 1.164033E−01 2.014289E+00 9.642688E+00 7.091920E+00 A14 6.207611E−03 −7.978158E−02 −1.586895E+00 −1.090871E+01 −9.005962E+00 A16 −2.705575E−03 3.131366E−02 7.693791E−01 7.737691E+00 7.011202E+00 A18 6.132612E−04 −6.653051E−03 −2.093885E−01 −3.141232E+00 −3.051727E+00 A20 −5.768452E−05 5.938009E−04 2.452765E−02 5.595529E−01 5.687071E−01 7th Surface 8th Surface 9th Surface 10th Surface 11th Surface k 9.880330E+00 −9.998139E+00 2.382937E+00 7.908520E+00 3.993866E−01 A4  1.227870E−01 −8.816667E−02 −9.302316E−02 8.243553E−03 9.888910E−03 A6  −1.824094E−03 1.321126E−01 4.445999E−02 −8.821769E−02 −3.244649E−02 A8  −7.566622E−02 −1.408390E−01 −9.394744E−03 1.005857E−01 2.246540E−02 A10 6.687344E−01 9.673623E−02 −5.473187E−03 −6.037781E−02 −7.903449E−03 A12 −2.030951E+00 −4.263617E−02 4.645052E−03 2.174843E−02 1.543717E−03 A14 3.212287E+00 1.205241E−02 −1.498614E−03 −4.824577E−03 −1.610545E−04 A16 −2.851026E+00 −2.119034E−03 2.553662E−04 6.433354E−04 7.658624E−06 A18 1.341106E+00 2.111367E−04 −2.327866E−05 −4.714330E−05 −8.141571E−08 A20 −2.560279E−01 −9.088146E−06 9.320959E−07 1.455259E−06 −8.070502E−10

The imaging lens in Example 2 satisfies conditional expressions (1) to (23) as shown in Table 5.

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Example 2. As shown in FIG. 4, each aberration is corrected excellently.

Example 3

The basic lens data is shown below in Table 3.

TABLE 3 Example 3 Unitmm f = 8.11 Fno = 2.40 ω(°) = 17.5 h = 2.56 TTL = 7.13 Surface Data i r d Nd ιd (Object) Infinity Infinity 1 (Stop) Infinity −0.8458 2* 1.9055 1.2185 1.535 55.69 (ιd1) 3* 127.7809 0.0790 4* 2.6626 0.3000 1.671 19.24 (ιd2) 5* 1.8364 0.5227 6* −3.3732 0.4922 1.614 25.59 (ιd3) 7* −21.7840 2.0740 8* −16.1600 0.3400 1.535 55.69 (ιd4) 9* 5.2630 0.2715 10*  −38.3493 0.8807 1.671 19.24 (ιd5) 11*  −4.2914 0.4272 12  Infinity 0.2100 1.517 64.20 13  Infinity 0.3838 n age Plane ConstituentLens Data Lens StartSurface FocalLength 1 2 3.605 2 4 −10.329 3 6 −6.565 4 8 −7.382 5 10 7.130 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface k −1.939492E−01 1.274648E−02 −3.118118E−01 −1.333085E+00 −7.654769E+00 A4  2.353183E−03 −6.584608E−02 −1.193395E−01 −6.439769E−02 9.067543E−02 A6  2.340319E−03 1.659053E−01 1.349921E−01 9.683063E−02 −2.716232E−01 A8  −8.724230E−03 −2.227372E−01 6.236344E−02 1.430563E−01 1.588394E+00 A10 1.623872E−02 1.880707E−01 −4.676992E−01 −6.550521E−01 −5.183845E+00 A12 −1.710201E−02 −9.821835E−02 8.029525E−01 1.448210E+00 1.048739E+01 A14 1.066761E−02 2.851998E−02 −7.386700E−01 −1.856286E+00 −1.329768E+01 A16 −3.923671E−03 −3.039126E−03 3.892009E−01 1.460682E+00 1.027345E+01 A18 7.879335E−04 −4.278610E−04 −1.108515E−01 −6.688877E−01 −4.422068E+00 A20 −6.748734E−05 1.023035E−04 1.331426E−02 1.389305E−01 8.132758E−01 7th Surface 8th Surface 9th Surface 10th Surface 11th Surface k 9.878465E+00 −9.998771E+00 2.040763E−01 7.907961E+00 6.357514E−01 A4  1.433454E−01 −6.750083E−02 −5.421218E−02 2.286156E−02 1.044889E−02 A6  −2.059356E−01 5.726445E−02 −1.957552E−02 −7.800440E−02 −3.165255E−02 A8  1.003820E+00 −6.202304E−02 2.936542E−02 6.444665E−02 2.168179E−02 A10 −2.731360E+00 5.507161E−02 −1.255083E−02 −2.659991E−02 −7.559197E−03 A12 4.581497E+00 −3.222748E−02 1.535609E−03 5.404292E−03 1.461337E−03 A14 −4.822704E+00 1.176153E−02 4.353171E−04 −2.748792E−04 −1.509269E−04 A16 3.084806E+00 −2.567769E−03 −1.655543E−04 −8.964975E−05 7.112294E−06 A18 −1.090528E+00 3.057146E−04 1.929158E−05 1.642503E−05 −7.468412E−08 A20 1.655328E−01 −1.520615E−05 −7.422102E−07 −8.447654E−07 −5.833524E−10

The imaging lens in Example 3 satisfies conditional expressions (1) to (23) as shown in Table 5.

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Example 3. As shown in FIG. 6, each aberration is corrected excellently.

Example 4

The basic lens data is shown below in Table 4.

TABLE 4 Example 4 Unitmm f = 8.11 Fno = 2.40 ω(°) = 17.5 h = 2.56 TTL = 7.13 Surface Data i r d Nd ιd (Object) Infinity Infinity 1 (Stop) Infinity −0.8467 2* 1.9032 1.2201 1.535 55.69 (ιd1) 3* 128.5200 0.0814 4* 2.6678 0.3000 1.671 19.24 (ιd2) 5* 1.8405 0.5149 6* −3.3745 0.4948 1.614 25.59 (ιd3) 7* −22.5209 2.0585 8* −13.9818 0.3400 1.535 55.69 (ιd4) 9* 5.1344 0.2838 10*  Infinity 0.8850 1.671 19.24 (ιd5) 11*  −4.6059 0.4272 12  Infinity 0.2100 1.517 64.20 13  Infinity 0.3838 n age Plane ConstituentLens Data Lens StartSurface FocalLength 1 2 3.600 2 4 −10.356 3 6 −6.526 4 8 −6.979 5 10 6.867 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface k −1.948727E−01 1.274648E−02 −3.162982E−01 −1.327622E+00 −7.627307E+00 A4  1.669056E−03 −6.392608E−02 −1.149729E−01 −5.765535E−02 9.362114E−02 A6  4.917442E−03 1.521925E−01 1.005910E−01 3.044281E−02 −2.981006E−01 A8  −1.420004E−02 −1.847388E−01 1.689105E−01 4.347724E−01 1.712801E+00 A10 2.316117E−02 1.313067E−01 −6.453472E−01 −1.416366E+00 −5.522374E+00 A12 −2.246843E−02 −4.740108E−02 9.787108E−01 2.757640E+00 1.106112E+01 A14 1.323657E−02 3.945578E−04 −8.439413E−01 −3.378854E+00 −1.392846E+01 A16 −4.663353E−03 6.408997E−03 4.261025E−01 2.620044E+00 1.072072E+01 A18 9.054558E−04 −2.197177E−03 −1.176550E−01 −1.189380E+00 −4.611406E+00 A20 −7.543825E−05 2.442517E−04 1.380501E−02 2.425262E−01 8.498238E−01 7th Surface 8th Surface 9th Surface 10th Surface 11th Surface k 9.878465E+00 −9.998771E+00 −2.278221E−01 7.907961E+00 7.718785E−01 A4  1.373227E−01 −6.114351E−02 −7.583022E−02 −2.236740E−02 −1.643883E−02 A6  −1.534121E−01 3.581298E−02 3.445127E−02 2.512887E−02 1.271762E−02 A8  7.605775E−01 −3.236442E−02 −3.717030E−02 −4.377586E−02 −1.057126E−02 A10 −2.029448E+00 3.311733E−02 3.454092E−02 3.795814E−02 5.190024E−03 A12 3.270412E+00 −2.232281E−02 −1.889444E−02 −1.828933E−02 −1.368957E−03 A14 −3.248621E+00 8.940946E−03 5.968675E−03 5.169240E−03 1.561833E−04 A16 1.916202E+00 −2.075222E−03 −1.079474E−03 −8.520552E−04 4.405767E−06 A18 −6.048751E−01 2.580235E−04 1.035829E−04 7.586242E−05 −2.580998E−06 A20 7.894907E−02 −1.326716E−05 −4.071026E−06 −2.820390E−06 1.627237E−07

The imaging lens in Example 4 satisfies conditional expressions (1) to (23) as shown in Table 5.

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Example 4. As shown in FIG. 8, each aberration is corrected excellently.

In table 5, values of conditional expressions (1) to (23) related to the Examples 1 to 4 are shown.

TABLE 5 Conditional- Example Example Example Example Expressions 1 2 3 4  (1) | r 7 |/f 1.63 1.10 1.99 1.72  (2) r 3/f 0.39 0.32 0.33 0.33  (3) r 4/T 2 4.04 3.23 3.51 3.57  (4) r 5/D 3 −8.62 −7.17 −6.85 −6.82  (5) r 3/r 4 1.60 1.46 1.45 1.45  (6) r 2/f 179.05 17.68 15.76 15.85  (7) r 6/f −4.46 −2.93 −2.69 −2.78  (8) r 8/f 0.37 0.74 0.65 0.63  (9) r 1 0/f −0.59 −0.52 −0.53 −0.57 (10) r 2/r 1/T 1 9428.87 903.88 849.18 829.82 (11) r 2/r 3 460.97 55.51 47.99 48.17 (12) r 2/r 3/r 1 0 −96.45 −13.05 −11.18 −10.46 (13) r 3/| r 7 | 0.24 0.29 0.16 0.19 (14) r 5/r 6 0.10 0.15 0.15 0.15 (15) r 5/| r 7 | −0.27 −0.40 −0.21 −0.24 (16) r 8/| r 7 | 0.23 0.67 0.33 0.37 (17) r 1 0/r 3 −1.52 −1.65 −1.61 −1.73 (18) r 1 0/r 4 −2.44 −2.41 −2.34 −2.50 (19) f 3/f −0.80 −0.85 −0.81 −0.80 (20) f 5/f 0.81 0.80 0.88 0.85 (21) f 5/D 5 7.54 7.37 8.10 7.76 (22) f 2/f 5 −1.36 −1.52 −1.45 −1.51 (23) ( f 4/f ) + −0.09 −0.02 −0.03 −0.01 ( f 5/f )

When the imaging lens according to the present invention is adopted to a product with the camera function, there is realized contribution to the low profile and the low F-number of the camera and also high performance thereof.

DESCRIPTION OF REFERENCE NUMERALS

-   ST: aperture stop -   L1: first lens -   L2: second lens -   L3: third lens -   L4: fourth lens -   L5: fifth lens -   IR: filter -   IMG: imaging plane 

What is claimed is:
 1. An imaging lens comprising in order from an object side to an image side, a first lens with positive refractive power having an object-side surface being convex in a paraxial region; a second lens with negative refractive power having an object-side surface being convex in a paraxial region; a third lens with negative refractive power having an object-side surface being concave in a paraxial region; a fourth lens with negative refractive power in a paraxial region; and a fifth lens with positive refractive power having an image-side surface being convex in a paraxial region, wherein the following conditional expression (1) is satisfied: 0.90<|r7|/f<4.00  (1) where r7: a paraxial curvature radius of an object-side surface of the fourth lens, and f: a focal length of the overall optical system of the imaging lens.
 2. The imaging lens according to claim 1, wherein an image-side surface of said second lens is concave in the paraxial region.
 3. The imaging lens according to claim 1, wherein an image-side surface of said third lens is convex in the paraxial region.
 4. The imaging lens according to claim 1, wherein the following conditional expression (2) is satisfied: 0.15<r3/f<0.75  (2) where r3: a paraxial curvature radius of an object-side surface of the second lens, and f: a focal length of the overall optical system of the imaging lens.
 5. The imaging lens according to claim 1, wherein the following conditional expression (3) is satisfied: 1.00<r4/T2<5.25  (3) where r4: a paraxial curvature radius of an image-side surface of the second lens, and T2: a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens.
 6. The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied: −12.00<r5/D3<−3.00  (4) where r5: a paraxial curvature radius of an object-side surface of the third lens, and D3: a thickness along the optical axis of the third lens.
 7. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied: 0.40<r3/r4<1.80  (5) where r3: a paraxial curvature radius of an object-side surface of the second lens, and r4: a paraxial curvature radius of an image-side surface of the second lens. 